package avl;

import map.Map;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

/**
 * @author gy
 * @date 2019/6/1 7:08
 */
public class AVLTree<K extends Comparable<K>, V> implements Map<K, V> {


    private Node root;
    private int size;

    public AVLTree(Node node, int size) {
        this.root = null;
        this.size = 0;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * 中序遍历 判定该树是否是二分搜索树
     *
     * @return
     */
    public boolean isBST() {
        List<K> keys = new ArrayList<>();
        inOrder(root, keys);

        for (int i = 0; i < keys.size(); i++) {

            if (keys.get(i - 1).compareTo(keys.get(i)) > 0) {
                return false;
            }
        }
        return true;
    }

    private void inOrder(Node node, List<K> keys) {
        if (Objects.isNull(node)) {
            return;
        }

        inOrder(node.left, keys);
        keys.add(node.key);
        inOrder(node.right, keys);

    }

    /**
     * 判断该二叉树是否是平衡二叉树
     *
     * @return
     */
    public boolean isBalanced() {
        return isBalanced(root);
    }

    private boolean isBalanced(Node node) {
        if (Objects.isNull(node)) {
            return true;
        }

        int balanceFactor = getBalanceFactor(node);

        if (Math.abs(balanceFactor) > 1) {
            return false;
        }

        return isBalanced(node.left) && isBalanced(node.right);
    }

    private int getHeight(Node node) {
        if (Objects.isNull(node)) {
            return 0;
        }
        return node.height;
    }

    private int getBalanceFactor(Node node) {
        if (Objects.isNull(node)) {
            return 0;
        }
        return getHeight(node.left) - getHeight(node.right);
    }

    @Override
    public void add(K key, V value) {
        root = add(root, key, value);
    }

    private Node add(Node node, K key, V value) {

        if (Objects.isNull(node)) {
            size++;
            return new Node(key, value);
        }

        if (key.compareTo(node.key) < 0) {
            node.left = add(node.left, key, value);
        } else if (key.compareTo(node.key) > 0) {
            node.right = add(node.right, key, value);
        } else {
            node.value = value;
        }

        //更新height
        node.height = 1 + Math.max(getHeight(node.left), getHeight(node.right));

        //计算平衡因子
        int balanceFactor = getBalanceFactor(node);

        //平衡维护
        if (balanceFactor > 1 && getBalanceFactor(node.left) >= 0) {
            //右旋转 LL
            return rightRotate(node);
        }

        if (balanceFactor < -1 && getBalanceFactor(node.right) <= 0) {
            //左旋转 RR
            return leftRotate(node);
        }

        //LR
        if (balanceFactor > 1 && getBalanceFactor(node.left) < 0) {
            //右旋转 LL
            node.left = leftRotate(node.left);
            return rightRotate(node);
        }

        //RL
        if (balanceFactor < -1 && getBalanceFactor(node.right) > 0) {
            //左旋转 RR
            node.right = rightRotate(node.right);
            return leftRotate(node);
        }

        return node;
    }

    private Node rightRotate(Node y) {

        Node x = y.left;
        Node t3 = x.right;

        x.right = y;
        y.left = t3;

        //更新height
        y.height = Math.max(getHeight(y.left), getHeight(y.right) + 1);
        x.height = Math.max(getHeight(x.left), getHeight(x.right) + 1);

        return x;
    }

    private Node leftRotate(Node y) {

        Node x = y.right;
        Node t2 = x.left;

        x.left = y;
        y.right = t2;

        //更新height
        y.height = Math.max(getHeight(y.left), getHeight(y.right) + 1);
        x.height = Math.max(getHeight(x.left), getHeight(x.right) + 1);

        return x;
    }


    private Node getNode(Node node, K key) {

        if (Objects.isNull(node)) {
            return null;
        }

        if (key.compareTo(node.key) == 0) {
            return node;
        } else if (key.compareTo(node.key) < 0) {
            return getNode(node.left, key);
        } else {
            return getNode(node.right, key);
        }

    }

    @Override
    public V remove(K key) {

        Node node = getNode(root, key);
        if (Objects.nonNull(node)) {
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    private Node remove(Node node, K key) {

        if (Objects.isNull(node)) {
            return null;
        }

        Node retNode;
        if (key.compareTo(node.key) < 0) {
            node.left = remove(node.left, key);
            retNode = node;
        } else if (key.compareTo(node.key) > 0) {
            node.right = remove(node.right, key);
            retNode = node;
        } else {

            if (Objects.isNull(node.left)) {

                Node rightNode = node.right;
                node.right = null;
                size--;
                retNode = rightNode;

            } else if (Objects.isNull(node.right)) {

                Node leftNode = node.left;
                node.left = null;
                size--;
                retNode = leftNode;

            } else {

                Node successor = minimum(node.right);
                successor.right = remove(node.right, successor.key);
                successor.left = node.left;

                node.left = node.right = null;

                retNode = successor;
            }
        }

        if (Objects.isNull(retNode)) {
            return null;
        }

        //更新height
        retNode.height = 1 + Math.max(getHeight(retNode.left), getHeight(retNode.right));

        //计算平衡因子
        int balanceFactor = getBalanceFactor(retNode);

        //平衡维护
        if (balanceFactor > 1 && getBalanceFactor(retNode.left) >= 0) {
            //右旋转 LL
            return rightRotate(retNode);
        }

        if (balanceFactor < -1 && getBalanceFactor(retNode.right) <= 0) {
            //左旋转 RR
            return leftRotate(retNode);
        }

        //LR
        if (balanceFactor > 1 && getBalanceFactor(retNode.left) < 0) {
            //右旋转 LL
            retNode.left = leftRotate(retNode.left);
            return rightRotate(retNode);
        }

        //RL
        if (balanceFactor < -1 && getBalanceFactor(retNode.right) > 0) {
            //左旋转 RR
            retNode.right = rightRotate(retNode.right);
            return leftRotate(retNode);
        }

        return retNode;
    }

    private Node minimum(Node node) {

        if (Objects.isNull(node.left)) {
            return node;
        }

        return minimum(node.left);
    }

    @Override
    public boolean contains(K key) {
        return Objects.nonNull(getNode(root, key));
    }

    @Override
    public V get(K key) {
        Node node = getNode(root, key);
        return Objects.isNull(node) ? null : node.value;
    }

    @Override
    public void set(K key, V newValue) {
        Node node = getNode(root, key);
        if (Objects.isNull(node)) {
            throw new IllegalArgumentException(key + "doesn't exist!");
        }

        node.value = newValue;

    }

    private class Node {

        public K key;
        public V value;
        public Node left, right;
        public int height;

        public Node(K key, V value) {

            this.key = key;
            this.value = value;

            left = null;
            right = null;

            height = 1;
        }
    }
}
